Topic 104 - Posture control in the central nervous system

Question 1

Words to include

Answer 1

• Hierarchical organization
• Ventral root alpha motorneurons
• Ventral root gamma motorneurons
• Upper motor system
  
  • Supraspinal level
  • Brain stem motor centers
    
    • Unconcious
    • Automatic
  • Normal posture
  • Complex voluntary movement
    
    • Movement initiation
    • Movement planning
    • Movement plan reconsideration
    • Movement execution
  • Cerebellar sytem
  • Basal ganglion system
• Lower motor system
  
  • Spinal level
  • Segmental, spinal movement execution
  • Flexor / extensor
  • Inhibition / activation
  • Final common pathway of Sherrington
  • Spinal alpha motorneuron
  • Spinal gamma motorneuron
• Antigravitational support
• Vestibular apparatus
  
  • Afferentation of posture
  • Antigravitational support
• Upper brain areas
  
  • Ventral horn
    
    • Alpha and gamma motorneurons
• Postural reflex
  
  • Antigravitational support
  • Center of mass
  • Relative position of body parts
  • Types in upper motor system
    
    • Tonic reflexes
      
      • Deiters nucleus
      • Vestibulospinal tract
      • Alpha and gamma motorneurons
    • Righting reflexes / supporting reflexs
    • Statokinetic reflexes
      
      • Rotation
      • Acceleration
      • Deceleration
      • Eye
      • Labyrinth
      • Otolith organ
    • Pacing and stepping-forward reflexes
      
      • Locomotion
  • Center of postural reflexes
    
    • Brain stem
      
      • Nucleus ruber
      • Nuclei of reticular formation
      • Deiters nucleus
    • Motor cortex
    • Cerebellum
    • Basal ganglia
    • Alpha motorneurons
    • Gamma motorneurons
• Transection of spinal cord
  
  • Spinal shock
    
    • Areaflexia
    • Hypotension
    • Poikilothermia

Pathways

• Vestibular apparatus
  
  • Pseudounipolar sensory neurons of Scarpa’s ganglion
  • Central axons
  • Four nuclei of the vestibular ganglion
    
    • Efferentation:
      
      • Nucl. oculomotorius
      • Cerebellum
      • Reticular formation
      • Alpha and gamma motorneurons
        
        • Spinal cord (cervical)
• Vestibular apparatus
• Lateral vestibular nucleus / Deiter’s nucleus
• Dorsal vestibular nucleus / Bechterew’s nucleus
• Medial vestibular nucleus / Schwalbe’s nucleus
• Ventral vestibular nucleus
• Vestibular ganglion
• Scarpa’s ganglion
• Oculomotor nuclei
• Cerebellum
• Reticular formation
• Vestibulospinal tract

Question 2

Division of the body concerning posture control

Answer 2

• Origin of posture and movement control are based on a hierarchial organization
• Neural system of the brain set the activity of the ventral root alpha and gamma motorneurons
• Control of posture and movement can be divided into two levels:
  
  1. Upper motor system
     
     • ​Supraspinal level
     • Determines normal posture and complex voluntary movements
     • Cerebellar and basal ganglion system plans and adjust mucsle tone
     • Voluntary movement
       
       • ​Movement initiation
       • Movement planning
       • Movement plan reconsideration
       • Movement execution
  2. Lower motor system
     
     • ​​Spinal level
     • Segmental, spinal movement execution
     • Flexor / extensor
     • Inhibition / activation
• Combined, UMS and LMS ensures antigravitional support

Question 3

Posture

Answer 3

• The basis of afferentation is formed by the vestibular apparatus
• Vestibulo-ocular system: cooperation of the eye and the vestibular apparatus
• Efferents determine tone of axial muscles, supporting body against gravitional and ensuring balance and localization of the body
• Upper brain areas control alpha and gamma motorneurons of ventral horn

Question 4

Postural reflexes

Tasks of postural reflexes

Answer 4

1. Ensure antigravitational support
2. Stabilization of the center of mass
3. Stabillity of the relative position of body parts

Question 5

Postural reflexes

Give the reflex types in the upper motor system

Answer 5

1. Tonic reflexes
2. Righting reflexes / supporting reflex
3. Statokinetic reflexes
4. Placing and step-forward reflexes / placing and hopping reflexes

Question 6

Postural reflex types

Tonic reflexes

Answer 6

• ​Role:
  
  • Stabilization of the center of mass
  • Maintaining the antigravitional posture
• Origin: Deiters nucleus
  
  • ​Reaches alpha and gamma motor neurons of the extremities via the vestibulospinal tract
• Deiters nucleus receives a direct inhibitory afferentation from:
  
  • Cerebellum
  • Cortex
  • Nucleus ruber
• Important roles in the afferentation:
  
  • Stretch receptors of the neck muscles
  • Joints of the spinal axis

Question 7

Postural reflex types

Righting reflexes / supporting reflex

Answer 7

• Reflex manitaining upright position
• Example: falling cat

Eye → neck muscles shoulder → trunk → pelvis → lower extremity

Question 8

Postural reflexes

Statokinetic reflexes

Answer 8

• Positioning the body during rotation, acceleration or deceleration
• Function is accomplished by:
  
  • Integration of the eye
  • Labyrinth
  • Otolith organ
• Source of reflex: fixation of the eye to the reference point for a longer period, then a fast shift to a new reference point (nystagmus)
  
  • The direction of nystagmus = direction of fast component

Question 9

Postural reflexes

Placing and step-forward reflexes / placing and hopping reflexes

Answer 9

• During locomotion arriving to the ground the extremities always move into the optimal position
• During jumping: sing a continuous series of posture reflexes close to the ground ensures an optimal landing position

Question 10

Pathways

Innervation of vestibular apparatus

Answer 10

• Innervation of vestibular apparatus: Pseudounipolar sensory neuorns of Scarpa’s ganglion​
  
  • ​The central axons of these neurons terminate in the four nuclei of the vestibular ganglion
• Efferentation of the vestibular ganglion:
  
  • ​Oculomotor nuclei
  • Cerebellum
  • Reticular formation
  • Alpha and gamma motorneurons of the spinal cord (mainly cervical)